Methods and devices for applying chemicals, such as herbicides and fertilisers, to plants are known. Such methods and devices include spraying and direct application methods and devices.
It is known that spraying-based methods may be suitable when large areas of target plants are involved. However, spraying methods may be unsuitable where target plants are interspersed with non-target plants. In this case, spraying-based methods of herbicide application may not be sufficiently accurate to apply a herbicide only to the target plants. This may result in damage of nearby non-target plants and contamination of the target plant environs.
Furthermore, spraying methods may also not be suitable under particular environmental conditions such as high wind or rain. Under these conditions, the herbicide may be either dispersed or diluted such that the concentration is not sufficient to be effective on the target plants and/or the herbicide may wash off or drift onto non-target plants and cause damage.
In light of the problems associated with spraying-based methods, a number of direct-application or contact type chemical applicator technologies have been developed in various attempts to address these problems.
For example, U.S. Pat. No. 4,357,779, to M. E. Maddock, describes a chemical applicator comprising a sponge applicator connected to a chemical reservoir wherein flow of chemical from the reservoir to the sponge applicator is controlled by a flow control valve.
U.S. Pat. No. 4,403,881, to J. H. Keeton, describes a hollow handled chemical applicator which comprises a chemical reservoir within the upper part of the handle. Chemical from the reservoir is supplied in discrete doses to a sponge applicator at the lower end of the device through a slit valve, which is openable in response to the operation of a button by a user of the device.
U.S. Pat. No. 4,716,677, to J. E Moore, describes a hand-held chemical applicator comprising a chemical applicator pad mounted between pincers or tweezers. The pincers or tweezers may then be used to grip a plant and thereby apply the herbicide to the surface of the plant gripped by the pincers.
Each of the herbicide applicators described above uses a sponge or absorbent pad to apply chemical to the surface of a plant. As such, the chemical is subject to wash-off during rainfall. This wash-off potentially leads to exposure of non-target plants or animals to the chemical and/or unnecessary contamination of the environment with the chemical.
Furthermore, wash-off potentially:                1. exposes non-target plants and animals to the chemical; and        2. reduces the concentration of the chemical on the target plant surface. This potentially reduces the effective dose of the chemical delivered to the target plant. The reduced effective dose of the chemical on the target plant surface may then necessitate repeat applications of the chemical and/or application of the chemical at a higher concentration. As would be appreciated, this potentially compounds the problems associated with chemical wash-off and increases the potential for non-target plant and animal exposure to the chemical.        
U.S. Pat. No. 5,724,765, to W. A. Wegner, describes a herbicide applicator comprising a pair of opposable jaws, each comprising an absorbent pad and a plurality of needles extending from each jaw into the pad. This device also comprises a herbicide reservoir which is connected by conduit to the absorbent pad on each jaw. When a plant is grasped by the jaws, the needles penetrate the surface of a plant. In this way, the herbicide, which is applied to the absorbent pads, coats the surface of the plant and then flows into holes produced in the plant tissue by the needles.
The device described in the Wegner patent does potentially lead to more effective utilization of herbicide, as wounding of the plant allows herbicide, from herbicide absorbent pads, to infiltrate the internal tissues of the plant. However, with the Wegner device, a significant amount of herbicide is still applied to the surface of the plant, via the absorbent pads. This surface-applied chemical is still prone to wash-off and thus can lead to exposure of non-target plants and animals to the chemical.
Methods for applying chemicals, such as pharmaceuticals, to animals are known. Such methods include injecting methods where a syringe is used to allow a pharmaceutical to directly flow from the syringe's reservoir down the barrel of a needle into the target tissue. It is also well known that injectable darts are used, which are based on the syringe technology.
Injecting methods may be suitable when a small number of specific target animals require an injectable pharmaceutical and when the target animal is accessible or lives in accessible media such as on land. However, injecting methods may be unsuitable where target animals are numerous, fast moving, interspersed with non-target plants and animals, remotely located, live in a medium such as below water or are out of reach and fast moving. In this case, injecting-based methods of pharmaceuticals may not be suitable for delivering the pharmaceutical to the target animals in an efficient and timely manner. Likewise, in situations where a large number of animals require specific doses of a pharmaceutical to be administered in a sterile manner, the syringe-style application devices have considerable limitations.
In light of the problems associated with injecting-based methods and devices, a number of direct-application or contact type chemical applicators have been developed in various attempts to address these problems.
For example, Patent Publication No. CN1415385 describes a miniature needle array sheet which supplies the pharmaceutical via said minipore array into the skin. Such devices can take the form of a transdermal patch to apply the pharmaceutical; however, such method and devices have limitations of applying pharmaceuticals to birds or water based animals, each patch has only a single use and used patches contribute to potentially toxic waste material within the environs when the patch is no longer attached to the target animal.
To overcome the deficiencies of, or to provide an alternative to, existing chemical methods and devices, the present invention provides a chemical applicator which substantially specifically delivers a chemical to the Internal tissues of the living organism in this way, chemical coating of the surface of organisms would be minimized and thereby the potential for wash-off of the chemical, and subsequent exposure of non-target plants or animals would also be reduced Substantially specific application of a chemical to the internal tissues of an organism would also potentially increase the effective utilization of a chemical, as the chemical could be delivered to the internal tissues of the organism where it is most effective, thus potentially decreasing the amount and/or concentration of a given chemical needed to achieve a desired outcome. Further, the application method can be rapidly reused to deliver the desired chemical to numerous organisms without the necessity to re-prime or re-sterilise the piercing elements.
Before turning to a summary of the invention, it must be appreciated that the above description of the prior art has been provided merely as background to explain the context of the invention. Accordingly, reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that this prior art forms part of the common general knowledge in any country.